The prior art shows numerous designs for light fixtures. These light fixtures generally have a light source, a reflector often integrally constructed with the body, and a front transmission plate which allows the radiation from the light source to escape and prevents the entrance of dust and other debris into the interior of the light fixture. These light fixtures are also often provided with vents to permit the escape of hot air produced by waste heat from the light source, and some designs have fans or blowers to forceably remove the hot air.
However, in most designs, the light source is permanently fixed and the front plate which transmits the radiation is also fixed. This creates difficulties for a photographer who has a need for quickly changing the type of illumination which he is using. Using light fixtures with a permanently fixed light source, he is required to store a large number of complete light units, one for each type of illumination he may need. Each individual light fixture will have to be separately mounted and aimed before it can be used.
There are many types of illumination which a photographer might require, and many kinds of light sources and filters which can be used to provide that illumination. For example, some light sources are very short in the time dimension, i.e, stroboscopic light sources, and some are very narrow in the frequency dimension, i.e., sodium or mercury lamps, while other may be very broad in those dimensions. Some light sources emit light of a very high color temperature in the blue or blue-white range, while others emit light from a lower color temperature in the yellow to red range. Some photographic films are more sensitive to, or are designed for use in conjunction only with light of a specified color temperature. In order for a photographer to have a range of suitable light sources to choose from, he was previously required to store multiple light units, each having a single type of light source.
It is also widely known that a transmission plate can be placed in front of the light fixture to modify the illumination in a variety of ways. For example, a harsh light can be transformed into soft illumination by the use of a diffusing plate made of ground glass or plexiglas. The diffuseness of the light can be modified by varying the surface roughness of the diffusing plate. The color of the illumination can be modified by using a colored filter, the strength of the illumination can be modified by using a neutral density filter, and the directional pattern of the exiting light can be modified with a fresnel lens if desired. Considering the numerous styles of transmission plates and light sources that a photographer might desire to employ, it becomes imperative to employ a design which allows interchangeable light sources and transmission plates. These are needs which are not met in prior art designs.
U.S. Pat. No. 3,375,366 shows a high intensity printing lamp having an integral body reflector, a light source, a front transmission plate, and a fan for cooling. However, this design does not provide for the use of an interchangeable light source or front transmission plate.
U.S. Pat. No. 2,831,104 shows a similar photographic illuminating means. In this design the light source can be replaced, but only by another light source having the same style of fitting on its base. Furthermore, replacing the light source would be a difficult and awkward job. The front transmission plate is also not easily changed.
U.S. Pat. No. 2,069,950 shows a surgical lamp which allows the light source to be easily replaced, but which does not accept different styles of light sources nor does it permit the transmission plate to be easily changed.